A catalyst system for diene polymerization using an organolithium compound in combination with a barium compound including barium stearate and barium t-butoxide, without showing how the barium compounds are made, is stated to provide random copolymers of certain dienes and mono-vinyl aromatic compounds, having a vinyl content of 7.8-13% and a trans content using Ba t-butoxide as high as 67.9% and using barium stearate as high as 70.5% (Examples 1 and 13, U.S. Pat. No. 3,629,213 (1971), Akira Onishi, Ryota Fujio, Minoru Kojima and Hiroshi Kawamoto, assignors to Bridgestone Tire Company Limited). Ryota Fujio, Minoru Kojima, Shiro Anzai and Akira Onishi (Bridgestone Tire Co., Ltd.), "Kogyo Kagaku Zasshi," No. 2 (1972), pages 447-453, in a somewhat similar disclosure show the reaction product of alkaline earth metals directly with active hydrogen containing compounds (apparently in benzene) and their use with organolithiums as catalysts. The use of barium stearate with an organolithium was said to provide 5.25%-59% trans for a butadiene-styrene copolymer. It was stated that barium stearate is scarcely effective and showed a maximum of 67.9% trans for SBR using barium t-butoxide and an organolithium.
U.S. Pat. No. 3,992,561 (I. G. Hargis, R. A. Livigni and S. L. Aggarwal; divisional U.S. Patents of the same Nos. 4,020,115; 4,033,900 and 4,048,427 have the same disclosure) discloses that barium t-alkoxide hydroxide salts in conjunction with organolithium compounds provide catalyst complexes useful in the solution polymerization of various vinyl or ethylenically unsaturated monomers. In particular, this patent discloses the preparation of polymers of butadiene and copolymers of butadiene and styrene having high trans contents (up to 80.4%) for the butadiene placements or segments. These polymers, also, exhibit a high viscosity and other desirable properties such as green strength and tack strength.
An object of this invention is to provide an improved barium t-alkoxide salt useful with organo-lithium compounds to form anionic catalyst complexes for polymerizing ethylenically unsaturated monomers and heterocyclic monomers.
Another object of this invention is to provide a method for making an improved barium t-alkoxide salt which is useful in conjunction with an organolithium compound to form anionic catalyst complexes which can cause polymerization of unsaturated monomers in solvent polymerization systems.
A further object of this invention is to provide a method for polymerizing unsaturated monomers or heterocyclic monomers using an anionic catalyst complex of an organo-lithium compound and a barium t-alkoxide salt.
These and other objects and advantages of the present invention will become more apparent to those skilled in the art from the following detailed description and working examples.